Condensation process of the formaldehyde-acetaldehyde type



' Patented Mar. 31, 1942 CONDENSATION PROCESS OF THE FORM- ALDEHYDE-ACETALDEHYDE TYPE Hermann Schulz, hTen-Isenburg, and Hans Wag- Frankfort-on-the-Main, signors, by m'esne assignments,

Germany, as-

to Chemical Marketing Company Inc., New York, N. Y.

No Drawing. Application August 29, 1939, Serial No. 292,404. In Germany September 10, 1938 Claims.

The present invention relates to a process of producing acrolein from formaldehyde and acetaldehyde.

In our copending U. S. application Serial No. 197,374 we have described a process for producing acrolein by conducting formaldehyde and acetaldehyde over a catalyst at elevated temperatures. While the process described in the aforesaid application has givensatisfactory commercial results, it has been found that the yields can be increased substantially provided the reaction products do not come in contact with certain materials. For example, it has been found that the material of' which the apparatus in which the reaction is carried out is constituted has a very great influence on the'smooth course of the reaction and on the yield. We have discovered that iron or aluminum exerts a very substantial detrimental eliect upon the yields. It would appear that in the presence of aluminum or iron a substantial decomposition of the reaction components is effected by iron or aluminum whereby the yields are considerably reduced. So far as we are aware, it has not been known to those skilled in the art that iron and ferrous alloys of the aforesaid type and aluminum had a detrimental effect upon condensations of this type. We have discovered that condensations such as that of formaldehyde and acetaldehyde to form acrolein, when carried out in an apparatus completely free of iron or aluminum or at least one in which those portions of the apparatus which come in contact with the reaction components at elevated temperature are not constituted of iron or aluminum, take place smoothly with yields appreciably greater than those obtained in the presence of iron or aluminum.

It is an object of the present invention to provide a process for producing acrolein whereby a smoother reaction takes place and the yields are appreciably greater than heretofore.

It is another object of the present invention to provide a process for producing acrolein by the reaction of formaldehyde and acetaldehyde in which the reaction components do not come in contact with iron or aluminum or alloys containing appreciable quantities of either metal. I

It is a further object of the present invention to provide a process for producing acrolein by the reaction of formaldehyde and acetaldehyde in the gaseous phase in the presence of catalysts in which the contact space and the superheater at least are constituted of material other than iron or aluminum or alloys having as a major constituent iron or aluminum.

The present invention also contemplates the provision of a process for producing acrolein by the catalytic reaction of formaldehyde and acetaldehyde in the vapor phase at elevated temperatures in which the reaction components do not contact iron or aluminum or alloys having as a major component either of the aforesaid metals.

The present invention further contemplates the provision of a process for-carrying on condensations of the formaldehyde-acetaldehyde type in the vapor phase in the presence of catalysts in which the reaction is carried out in the absence of substantial amounts of iron and aluminum.

Other objects and advantages of the present invention will become apparent from the following description.

Broadly stated, in accordance with the principles of the present invention those portions of the apparatus in which the catalytic condensation of aldehydes to form substances of the acrolein type at elevated temperatures are constituted of suitable materials. other than iron or aluminum or materials having as a major component either iron or aluminum. It is particularly important that in an apparatus for the catalytic condensation of aldehydes such as acetaldehyde and formaldehyde to form acrolein, the contact space itself, the superheater, connecting pipes and valves be constituted of materials other than iron or alumi-.

num.

In order that those skilled in the art may have a better understanding of the present invention, the following illustrative list of suitable materials is provided. Those portions of the apparatus instead of the pure metal. In addition, alloys containing the aforesaid metals together with other substances, for example, silicon, may like wise be used. Such alloys may be the bronzes or alloys containing silicon. We have found that the iron-chromium-aluminum alloy known to those skilled in the art as Sichromal may be used. Furthermore, the apparatus may be constructed wholly or in part of metal coated on the surfaces exposed or coming in contact with the reaction components with a suitable enamel. Glass lined apparatus or apparatus in which those portions heated to elevated temperatures coming in contact with the reaction components are coated with a glass of suitable softening point likewise provide the advantages over the prior art processes aflorded by the presentinvention.

While all of theabove materials may be used,

we have found that it is preferable to use copper or its alloys. 5

As illustrative of the eflect of replacing apparatus constituted wholly or in part of iron or aluminum by apparatus constituted of copper at least in those portions coming in contact with the reaction components at elevated temperatures, the following comparison of yields obtained in both apparatus, is provided. In both tests 490 kg. of formaldehyde 30% were reacted with 220 kg. of acetaldehyde in the presence of a silica-gel catalyst at 300 C. The "yield of in accordance with the principles of the present invention, using the same quantities of reactants and substantially the same reaction conditions, the yield of acrolein of the same grade was'84.5% of theorie. In addition to obtaining increased yields of acrolein of substantially the same grade,

the reaction proceeded with much greater smoothness.

Although the present invention has been described in conjunction with certain embodiments thereof it is to be understood that variations and modifications may be made as those skilled in the art will understand. Such variations and modiflcations are to be considered within the purview of the specification and the scope of the appended claims.

We claim: 7

1.- A process for producing acrolein which comprises catalytically condensing formaldehyde and acetaldehyde in the vapor phase at temperatures high enough to' maintain said aldehydes in 40 vapor phase, and preventing the vapors from coming into contact with iron and aluminum.

2. In the process for producing acrolein by the catalytic condensation of formaldehyde and acetaldehyde in the vapor phase at temperatures high enough to maintain said aldehydes in vapor phase, the improvement which comprises preventing the reaction components from contacting at said temperatures with a material selected from the group consisting of iron and aluminum.

3. In the process for producing acrolein by catalytically condensing formaldehyde and acetaldehyde in the vapor phase at temperatures high enough to maintain said aldehydes in the vapor phase, the improvement which comprises reacting the formaldehyde with the acetaldehyde substantially in the absence of iron and aluminum.

4. In the process for producing acrolein by catalytically condensing formaldehyde and acetaldehyde in the vapor phase at temperatures high enough to maintain said aldehydes in the vapor phase, the improvement which comprises reacting the formaldehyde with the acetaldehyde in contact only with a metal having copper as a major component.

. 5. In the process of producing acrolein by catalytically condensing formaldehyde and acetaldehyde in the vapor phase at temperatures high enough to maintain said aldehydes in the vapor phase,, the improvement which comprises reacting the formaldehyde with acetaldehyde to obtain reaction products and maintaining said formaldehyde, acetaldehyde and reaction products while at said temperatures in contact only with material selected from the group consisting of copper, silver, nickel, chromium. ceramic materials, silicious enamels, alloys of copper and alloys constituted principally of at least one of the aforesaid metals.

HERMANN HANS WAGNER. 

